1. Field of the Invention
The present invention is generally in the field of transmission lines. More particularly, the invention is in the field of transmission lines on circuit boards.
2. Background Art
Circuit boards including transmission lines, such as transmission lines configured as differential pairs, are commonly utilized in data transmission in devices, such as optical and Ethernet devices, in communications systems. In a circuit board utilized in a communications system for data transmission, for example, a pair of transmission lines can be formed on a top surface of the circuit board, a ground plane can be formed on a bottom surface of the circuit board, and a dielectric material, such as Flame Retardant 4 (FR-4), can be utilized to insulate the transmission lines from the ground plane. However, as the speed of signals traversing the transmission lines increase, the use of a dielectric material such as FR-4 can result in, for example, increased insertion loss and dielectric loss, resulting in a loss of transmitted signal energy.
A conventional approach for reducing dielectric loss in circuit boards includes utilizing a polytetrafluoroethylene (PTFE)-based dielectric material, such as “Rogers®” (a PTFE-based material manufactured by Rogers Corporation). A PTFE-based material can have a lower dielectric loss and a lower insertion loss than FR-4, which results in a reduced signal energy loss at high data transmission speeds. Although the use of a PTFE-based material can result in reduced insertion loss and dielectric loss for high-speed signals traversing the transmission lines, PTFE-based materials can be significantly more expensive than FR-4, which can undesirably increase manufacturing cost. Also, PTFE-based dielectric materials can be less reliable than FR-4.